Use CMake command create_symlink instead of calling ls -s,

because it is resistant to repeated calls.

This solves FTBFS with CMake >= 3.11, because in the case of update
a library file, as a result of a tdelfeditor call, this will cause
repeated calls for targets that are dependent on the library.

As a result, it is now possible to use call based on POST_BUILD,
and there is no need to distinguish the way of calling created in
the commit e22f5ace4a.

Signed-off-by: Slávek Banko <slavek.banko@axis.cz>
(cherry picked from commit e1b441631c)

modules/TDEMacros.cmake

@@ -1263,22 +1263,12 @@ macro( tde_add_library _arg_target )
         get_target_property( _soversion ${_target} SOVERSION )
         set( _soname "${_soname}.${_soversion}" )
       endif( )
-      if( NOT _exclude_from_all )
-        add_custom_command(
-          OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}"
-          COMMAND ln -s ${_soname} "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}"
-          DEPENDS ${_target}
-        )
-        add_custom_target(
-          ${_target}+base-so ALL
-          DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}"
-        )
-      else( )
-        add_custom_command(
-          TARGET ${_target} POST_BUILD
-          COMMAND ln -s ${_soname} "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}"
-        )
-      endif( )
+      add_custom_command(
+        TARGET ${_target} POST_BUILD
+        COMMAND ${CMAKE_COMMAND} -E create_symlink
+          "${_soname}"
+          "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}"
+      )
       install( FILES "${CMAKE_CURRENT_BINARY_DIR}/${_soname_base}" DESTINATION ${_destination} )
     endif( )